There are many industrial applications for devices which pulverize organic materials such as waste food products, inorganic materials such as mineral ore, and the like. As regards organic waste materials, the advancement of modern society has brought with it the problem of disposal of its wastes. A particular problem has been experienced with the disposal of solid wastes remaining following the processing of food, both at food processing plants and at large institutional kitchens. Significant health and environmental hazards can arise from the use of "dumpsters" and solid waste landfills, since such disposal devices tend to attract pests such as rodents and insects, as well as causing foul odors.
It has been found that food wastes can be disposed of more efficiently or even recycled as animal food or the like if the waste is comminuted into the form of a liquified colloidal suspension. To that end, various comminuting devices have been developed. These devices range from the common household garbage disposal in the kitchen sink to large industrial units. For example, U.S. Pat. No. 4,120,457 discloses a pulverizer employing a pivotally mounted hammer on a horizontally rotating plate which operates in relation to a fixed cylindrical surface of variable height lands and grooves, and thereafter, the food is passed between horizontally arranged and relatively rotating sets of lands and grooves mounted in complementary fashion or annular extensions of the rotating plate and the fixed housing.
In many comminuting devices, rotating members such as teeth or lands pass in close proximity to fixed members so that food pieces are caught between corners or edges of the two members and are shredded or broken apart. U.S. Pat. Nos. 4,387,858; 2,824,702; 4,082,229; 3,480,213; and 3,314,617 show shuch shredding members in comminuting units. In other such units, the rotating lands or teeth have been provided with a somewhat stepped shape surface, generally oriented to face the stationary members. Such devices are disclosed in U.S. Pat. Nos. 3,083,922; 2,819,847; and 4,134,555.
Despite these attempts, comminuting technology prior to the present invention has not reduced food wastes to liquified colloidal form as efficiently or completely as possible.
Another area in which there is a need for efficient and effective material pulverization is in the processing of metal ores, for example, iron ore.
Metallic ores such as gold, silver or copper are normally found on or near the surface of the ground in a fairly pure state; therefore, little processing is necessary. Iron ore, on the other hand, is found embedded in the earth and must be extracted from the soil and surrounding rock before it can be used productively.
The procedure used to separate iron ore from its surrounding impurities typically involves mining the ore, usually from an open pit, crushing the ore into fragments, and magnetically separating the ore fragments from the fragments of solid and rock.
It has become evident that the iron deposits in the United States are no longer yielding as much purified iron per ton. This is due to the fact that the remaining ore deposits contain a lower percentage of iron. A more efficient method of iron ore extraction is therefore needed. Pulverization of the ore into smaller particles would provide for a greater recovery of these lower amounts of iron. Therefore, an apparatus is needed which can efficiently and economically pulverize ore into very fine particles.